Hydraulic blank holder



D@n 11s, 192s. y 1,696,141

W. FERRIS HYDRAULIC BLANK HOLDER v Filed Nov.18, 192e ys .sheets-snee''1' F15. j. /z

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A TTORNEY.

Decn 1s, 192s. 1,696,141

' w. FERRls HYDRAULIC BLANK HOLDER Filed NOV. 18, 1926 5 Sheets-Shea 2De1s,19zs. 1,696,141

W. FERRIS HYDRAULIC BLANK HOLDER F11-ed 11011.18. 192s 1 s sneetssnee 3HHHHHHHHHHHHHHH BY I/I/L T55' @55.15.

@bw-Ml ATTORNEY.

rPatented Dec. 18, 1928.

UNITsD s'ra'ilazsI 1,696,141 PATENT OFFICE.:

WALTER FEB/BIS, OE MILWAUKEE, WISCONSIN, ASSIGNOR TO THE OILGEAR GOM- ;lPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

Y y HYDRAULIC BLANK HOLDER.,

This-invention relates to hydraulic blankv holders for draw presses.

Blank holders for this purpose ordinarily include a` pressure ring whichfunctions to apply the required gripping pressure to the blanks duringthe draw stroke and to strip the blank from the die during the returnstroke. It is common practice to employ an air pad or springs foroperating the presl0 sure ring, but such devices are objectionablebecause of their inherent resiliency and the consequent jump that occursat the instant the blank is freed from the die. t Mechanical devicescapable of positive action have been resorted to with a view toeliminating the jump, but such devices are not entirely satisfactorybecause of the complicated toggle movements ordinarily required toattain correct action of the ring. In'my copending application SerialNo. 115,487, filed June-12, 1926, l have described a hydraulic blankholder in which the above objections have been eliminated and which maybe readily applied as a unit to standard types of presses withoutalteration. 'In the lank holder therein described however the blankgripping pressure is established by controlling the escape of liquidfrom the pressure cylinder during the draw stroke, and the resistanceoffered to this escape entails a waste of power and a consequent heatingof the liquid.

j One. object of the present invention is the provision of a hydraulicblank holder so designed. as to overcome theobjections above noted.

Other more specific objects and advantages will appear from thefollowing description of several embodiments of the invention.

In the drawings Figure 1 lis a vertical sectional view of a blank holderconstructed in accordance with the present invention and shown appliedto a ress of standard form. l

igs. 2 and 3 are similar views illustrating the positions of the partsduring successive stages of a drawing operation.

Figs. 4 and 5 are similar fragmentary views of a blank holder ofslightly different form, embodying the present invention.

Fig. 6 is a similar view of a third form of blank holder embodying thepresent invention.

The blank holder shown in Figures 1 to 3 comprises a pressure sustainingmember in the form of a casting 10 supported beneath Application filedNovember 18, 1926. Serial No. 149,155.

thebed 11 of a press so as to move with the reciprocating ram 12. lnthis instance the casting 10 is carried by a pair of heavy rods 13,adjustably fixed at their lower ends to the casting and anchored at,their upper ends in the ram 12. A piston 14 rigidly connected with andcarried'by the casting 10 is closely fitted for relative reciprocationwithin an appropriate cylinder 15, carried by a pressure plate 16, whichis guided by the rods 13. Any appropriate means such as a stem 17,projecting upwardly from the cylinder 15 and threaded into the pressureplate 16, provides an adjustable connection between the plate andcylinder. The plate 16 is yieldably urged upwardly against the lowerface of the bed plate 18 of the press by appropriate means such assprings 19, surrounding the rods 13 and interposed between the plate 16and casting 10. The pressure plate 16 conmined by the connection 26 withan appropriate overflow pipe 27. The cylinder 15 is provided with aseries ofinlet ports 28, open to the reservoir, and controlled by thepiston 14. The piston in this instance is formed intermediate its ends,with an annular channel 29 which'is always in open communication withthe interior of the cylinder through appropriate ducts 30, and, at itsupper end, with an appropriate peripheral shoulder 31; closely fitted inthe cylinder and arranged to cover and thereby close the ports 28, whenthe piston and cylinder assume the positions shown in Figures 2 and 3.

Liquid is supplied to the cylinder 15 from a second source comprising apump 32 ref-1 erably of a variable delivery type capab e of `deliveringmeasured quantities of 1i uid to the cylinder. The pump shown is fu lydescribed in my prior Patent, No, 1,558,002, issued October 20, 1925. Itwill therefore suiiice here to say that it is driven at constant Aportsare closed the speed through appropriate means such as a pulley 33, anddelivers liquid through a delivery pipe 34 at a definite rate determinedby the setting of the control handle 35. The liquid is supplied from asump provided in the base 36 of the pump casing. In this instance pipe34 is connected to a passage 37 in the piston 14, leading to theinterior of the cylinder 15, an appropriate relief valve 38 beingprovided for determining the maximum pressure wthin the delivery pipe.Appropriate swivel connections 39 are preferably provided in the supplypipe in order to permit freev movement of the casting 10 to which thepipe is connected. The overflow pipe 27 is preferably connected to thesump in the base 36 of the pump easing through a flexible hose 40. Thecontrol handle 35 is ordinarily so adjusted as to cause the pump todeliver only very small quantities of liquid to the cylinder 15.

A brief description of a typical drawing operation will now be given.Figure 1 illustrates the relative positions of the parts prior to anoperating cycle. The ram 12, and consequently the casting 10, are inelevated position, so that the dies 23 and 24 are se arated, the ring 22is in upper work receiving position, the pressure plate 16 bears againstthe lower face of the bed plate 18, and the piston 14 is disposed withinthe upper end of the cylinder 15, so that the interlor of the cylinderis open to the reservoir` 25 through ports 28, channel 29 and ducts 30.

Then during the down stroke ofthe ram 12, the casting 10 moves.downwardly therewith, but the pressure plate 16 remains in the elevatedposition shown until the upper die 24 engages the work, as indicated inFigure 2. This relative motion between the casting 10 and plate 16produces a corresponding motion between the piston 14 and cylinder 15,causing the shoulder 31 of the plston to approach the ports 28 and toactually cover and close the same an instant before the die 24 engagesthe blank. During this relative motion between piston and cylinder, thecylinder has been maintained flooded by the admission of liquid from thereservoir 25 through ports 28, channel 29 and ducts 30 and from the pump32 through the passage 37, and until the ports t28 are closed by theshoulder 31 the pressure in the cylinder does not exceed atmosphericpressure. After the ump continues to deliver liquid to the cy inderthereby immediately building up pressure therein to a deree depndentuponthe setting of the reief valve 38. This increased pressure istransmitted thru the pressure plate 16 and pins 20 to the ring 22 t0establish a blank holding pressure between the ring and the advancingdie 24.

This clamping pressure is maintained during the continued-down stroke ofthe ram 12,

die 24 and casting 10 until the drawing opleration is completed, thering 22, pins 20,

and pressure plate 16 being forced downwardly by the advance of'the die24 during,r this period. Figure 3 illustrates the )ositions of the partsat the end ot the draw stroke. It will be noted that during this drawportion of the strokcthere is no relative motion between the piston andcylinder, so that the amount of liquid delivered by the pump need onlybe sufficient t0 maintain pressure within the cylinder against leakagelosses.

During the upward or return stroke of the ram 12, die 24, and casting10, the pressure is maintained in the cylinder 15, and the pressureplate 16, pins 20, and ring 22 are carried upwardly by the casting 10until the pressure plate again engages beneath the bed plate 18. Thering 22 thus serves to strip the formed work piece from the lower die23. The continued upward movement of the casting 10, after the pressureplate 16 has engaged the bed plate 18, forces the piston 14 upwardlyinto the cylinder 15 and the parts return to their respective positionsshown in Figure l. This upward movement of the )iston again opens theorts 28 so that the iquid within the cylin er 15 is free to escapetherethrough into the surrounding reservoir.

In the blank holder shown provision is madeby which a greater pressureis available within the cylinder 15 during the stripping operation thanduring the draw stroke so as to obtain a greater stripping force. Thisis desirable because of thetremendous force sometimes found necessary top ry the work loose from the die. "This is accomplished in this instanceby interposing an appropriate check valve 41 in the pump delivery linebetween the relief valve 38 and passage 37. This valve prevents theescape of liquid from the cylinder to the valve 38, so as to trap thebody of liquid within the cylinder 15 during the upward stroke of thecasting l0. In order p to relieve the cylinder of excessive pressuresand to permit the required relative motion between the piston andcylinder to uncover the ports 28, when the pressure plate 16 strikes thebed plate 18 on the upward return stroke, arelief valve 42 is provided.This f valve is connected to the passage 37 throufrh an appropriatepassage 43, and is ordinarily adjusted to open at a pressureconsiderably above the pressure at which the valve 38 will o en.

pThe blank holder shown in Figures 4 and 5 is similar in many respectsto that just described. It includes a pressure sustaining member in theform of a casting 10', supported beneath the bed 11 of the press by rods13 xed to the reciprocating ram of the press, and a pressure plate 16supporting the usual knock-out pins 20. In this 1nstance apiston 14adjustably fixed to the pressure plate cooperates with a cylinder 15carried by the casting, and the reservoir shown in Figures 1, 2 and 3has been eliminated.

A The cylinder shown in Figures 4 and 5 is supplied with liquid from. apump, such as that hereinabove described, through pipes 84 and 37', andan overflow pipe 27 leading back to the pump determines the level ofliquid within the upper open end of the cylinder. The piston 14 isprovided with a peripheral channel 29 and shoulder 31' which cooperateswith ports 28 in the cylinder wall in a manner similar tothathereinabove described. In this instance each port 28 communicatesthrough a pipe 44 with the upper end of the cylinder and through ducts30 with the lower end of they cylinder. The piston is preferably rovidedwith a tail rod 45 of substantially t e same diameter as the stern 17,so that the two sides of the piston are of substantially the same area,and the flow of liquid from one end to the other of the cylinder, due tomovements of the piston therein will not materially change the level ofthe liquid within the upper end of the cylinder. A check valve 41 isinterposed between the pipes 34 and 37', and two relief valves 38 and 42are connected with pipes 34 and 37', respectively, which function insubstantially the same manner as valves 38 and 42 hereinabove mentioned.

The arrangement is such that during the downward idle stroke of the ramthere is a relative motion between the piston 14 and cylinder 15 fromthe position shown in Figure 4 toward that shown in Figure 5. Duringthis movement liquid is admitted to the lower end of the cylinderthrough the pump delivery pipe 37 and the pipes 44 leading from theupper end thereof, until the ports 28 are closed by the shoulder 81 onthe piston. This occurs as the reciprocating die strikes the workandthereafter pressure is maintained within the cylinder, by thedelivery of liquid thereto from the pump, thereby maintaining a blankgripping pressure during the entire draw lstroke in a manner similar tothat hereinabove described. During the return stroke pressure issimilarly maintained in the. cylinder so as to effect a strippingoperation, after which the piston and cylinder return to the positionsshown in Figure 4.

The blank holder shown in Figure e is Similar to that shown in 'Figures1, 2 and 3 except that several sets of pistons 14 and 15 are employed.Two or more of such sets are ordinarily employed in those instanceswhere the blank is unusually llarge. The blank holder shown in thisfigure includes a single reservoir 25 carried by the casting 10 andsurrounding the several sets of piston and cylinder assemblies. Anoverflow pipe 27 determines the liquid level in the reservoir.

check valve 41 and pressure relief valves 38 and 42 function in a mannersimilar to the check valve 41 and relief valves 38 and 42 hereinabovedescribed. The operation of the pistons and cylinders is substantiallythe same. asthat hereinabove described.

Various changes may be made in any of the embodiments of the inventionhereinabove described without departing from the invention as defined inthe appended claims.

I claim:

1. In a draw press having cooperating dies a blank holder thereforcomprising a blankv holding and stripping member cooperating with one ofthe dies to grip the blank therebetween, a pressure sustaining memberconnected with the last mentioned die, hydraulic means for transmittingpressure between said members, means responsive to relative movementbetween the dies for controlling said pressure during the draw stroke,and means for effecting an increased pressure in said hydraulic meansduring the stripping operation.

2. In a draw press having fixed and mova ble dies a blank holdertherefor comprising a blank holding and stripping member cooperatingwith the movable die, a pressure sustaining member movab-le with themovable die, hydraulic means for transmitting pressure between saidmembers,` means responsive to movement of said 'movable die forcontrolling said pressure during the draw stroke, and means foreifecting an increased pressure i-n said hydraulic means dur.- ing thestripping operation.

3. In a draw press the combination of a relatively movablev blankholding and strip `ping member and cooperating die, hydraulic pressureapplying means associated therewith and normally operable to permitfree. relative movement therebetween, control means for said pressureapplying means automatically operable to effect a clampingpressurebetween said die and member during the dra-w stroke, and /meansfor edecting an increased pressure within said hydraulic means duringthe stripping operation.

l 4.L In ai draw press the combination of a relatively movable blankholding member and cooperating die, a pressure sustaining memberconnected with said die, a cooperating piston and cylinder between saidmembers freely movabl'erelative to each other during relative movementbetween said blank holding member and die, a liquid reservoir formaintaining a lsolid body of liquid in said cylinder during suchmovement, means operableto confine the liquid within said i cylinder tothereby effect a working pressure therein during the draw stroke of thepress for maintaining said pressure against leak-` age losses.

5. In a draw press the combinationof a relatively movable blank holdingmember and cooperating die, a pressure sustaining member connected withsaid die, a. cooperating piston and cylinder between said members freelymovable relative to each other during relative movement between saidblank holding member and die, a liquid reservoir for supplying liquid tosaid cylinder, and a pump connected with said cylinder to establish aworking pressure therein during the draw stroke of the press to therebyestablish a work clamping pressure between said blank holding member anddie during the draw stroke.

6. In a draw press the combination of a reciprocating ram, a pressuresustaining member movable with said ram, a. blank holding member, acooperating piston and cylinder between said members, a pump fordelivering liquid at a predetermined rate to said cylinder, means forfreely admitting and dischar g li uid to and from said cylinder duringthe idle port-ions of the ram movements, and means for confining theliquid within said cylinder during the working portions of the rammovements to provide a working pressure therein.

7. In a draw press the combination of a bed plate, a reciprocating ram,cooperating dies on said plate and ram, a work holding and strippingring, a. pressure plate beneath said bed plate for supporting said ring,a pressure sustaining member beneath said pressure plate and carried bysaid ram. a cooperatin piston and cylinder between said pressure p ateand member freely movable during movement of said ram toward and fromsaid ring, means for supplying liquid pressure to said cylinder to applya blank holding pressure to said ring during the draw stroke of the ramand a check valve between said cylinder and said pressure sup- 9. In adraw press having a pair of cooperating dies, a blank holding membercooperating with one of said dies to grip a blank therebetween, apressure sustaining member connected with said last mentioned die,hydraulic pressure transmittin means between said members, a pump forelivering liquid to said means, a check valve between said pump and saidmeans, means for determining pump delivery pressure to thereby determinethe blank gripping pressure, and separate means for determining thefluid pressure in said pressure transmitting means to thereby determinethe blank stripping pressure.

l0. In a blank holder for draw presses and the like comprising a blankholding member, a pressure sustaining member, a cooperating piston andcylinder between said members, means for delivering liquid to saidcylinder, a port in said cylinder normally permitting a free admissionand dischar e 'of liquid to and from said cylinder, an said means, meanscontrolled by movement of said piston for closing said port to therebysubmit said piston and cylinder to the pressure of said liquid deliverymeans, and a pump for delivering liquid to said cylinder at a.predetermined rate.

In witness whereof, I hereunto subscribe my name this 19th day ofOctober, 1926.

WALTER FERRIS.

